Commodities Prices are Falling. Really.

After a drought-related surge, agricultural commodities from coffee to corn are in a multimonth-bear market.

Although it may not be reflected in your supermarket bills, prices for many of the items on your grocery list are in decline on the wholesale level. The trend in the venerable Commodities Research Bureau (CRB) index of commodities futures prices is down since September and down more than 18% since its all-time high set in April 2011.

To be sure, trends change, and within those trends there are periods of movement in the opposite direction. The index is up roughly 1.2% for January thanks to strength in grains such as...